Sydney police are searching for a group claiming to be psychics who have defrauded at least four people of more than $500,000.

The group of two women and two men have been advertising psychic readings by a woman called 'Nina' in local newspapers, then asking their customers for possessions they say need to be cleansed from a curse.

Detective Inspector Jim Stewart says the customers are then told the money in their bank accounts requires cleansing too.

"They take that money and take it away from the victim with the agreement that money will be returned to the person once it's been cleansed," he said.

"The person returns in five or six days and obviously the money is not there.

"These people are preying on people who have a depression problem, a family problem, and they say they can fix it for them and that's how they get sucked in."